2-Component Combination Motor Controller

2-Component Combination
Motor Controller solutions
for North America
The complete range of contactors, efficient motor-starters
and variable speed drives for
the motor circuit. New simple to install solutions based
on clever communication.
Technical Paper
Dipl.-Ing. Wolfgang Esser
Contactors DIL
Reliably and safely controlling,
switching and managing
power. In industry, in buildings
and in machine construction.
Innovative protection concepts.
With built-in diagnostics and
communication functions.
Housed in modern switchboard
Circuit-breakers NZM
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2-Component Combination Motor Controller
solutions for North America
– fuseless motor starters without separately mounted overload relay –
Differing styles of motor starters
Everyone would agree that motors are
by far the most important pieces of
equipment in the machine tool and
panel building industry. This paper will
deal mainly with modern aspects of
switching and protecting asynchronous
or squirrel-cage motors, still the primary
workhorses of the industry. There are
essentially 2 traditional approaches
involved in switching and protecting
such motors. One uses fuses as the
primary overcurrent protective device.
The other is fuseless, and relies on
motor protective switches or circuit
breakers as the core protective element.
Both versions feature a separately
mounted overload relay as a means to
protect the motor against running
overloads, and both are typically
combined with motor switching and HP
rated motor contactors to provide
longer life and remote control
operational capabilities for the motor
starter. Fuseless solutions have the
advantage that they are inherently
independent of local fusing styles and
conditions, which can vary greatly from
market to market, and they also would
permit, in most cases, a relatively quick
resetting of the circuit without
exchange of components once the
cause for the fault had been eliminated.
An additional safety related consideration of significant importance would
be that the fuseless protective device
would operate to open all 3 poles
simultaneously in the event of a fault,
whereas fuses operate independently
and are thus more prone to allow single
phasing conditions to develop in a
The combination of a motor protective
device, or a circuit breaker, and a motor
switching contactor also lends itself
well to different levels of component
protective co-ordination testing, such as
been popularized for years in the IEC/
EN 60 947 standard, and of late as well
in the recently introduced and
comparable North American UL 60 947
industrial control standard.
Co-ordination levels are indicators of
the protection afforded to the circuit
and a determination as to whether or
not, in the event of fault, welding and
inoperability of the contactor are
permissible outcomes.
In the IEC world, the choice between a
motor protective switch or a circuit
breaker can often be made simply
based on the size and rated current of
the motor. In North America, both types
of components fall under markedly
different product standards (UL 508
resp. UL 489, or CSA-C22.2 No.14 resp.
CSA-C22.2 No. 5-02), which ultimately
also impacts the application range of
both components when they are used
as protective devices in branch circuits.
Typically, the equipment would be
subject to different construction
requirements as well, such as the need
for circuit breakers to feature the larger
electrical clearances of distribution
equipment. In the IEC world, the
situation is different, with many
manufacturers of motor protective
switches more apt to commonly refer to
their equipment as circuit breakers,
making the line between both types
decidedly more blurry. Motor protective
switches represent a particularly
significant product grouping within
Moeller, both from a technical and
manufacturing volume point of view.
Moeller actually prefers to use the more
precise term „Motor Protective Switch“
for their own devices, since they are
optimally designed for motor
protection and generally available in
relatively low current ranges, i.e. up to
appr. 65A, to cover the large majority of
industrial motors. These components
are also phase failure sensitive per the
requirements of IEC/EN 60 947, which is
considered a premium feature for
motor protection applications. Moeller
is justifiably considered a pioneer in the
field of motor protective switch design,
to the point where the PKZM brand
reference in the electrical industry is
often used as an eponym or generic
term to refer to products from all
makes in this category.
The IEC product standard pertaining to
a molded case circuit breaker, IEC/
EN 60 947 Part 2, does not contain any
specific testing provisions for motor
protection. One needs to combine
certain test requirements from an
additional product standard, IEC/
EN 60 947-4-1 for contactors, overload
relays and motor starters, in order to
legitimize the device as a „Motor
Protective Circuit Breaker“, or large
motor protective switch. A similar
situation exists in North America,
whereby the applicable product
standards for molded case circuit
breakers and switches, i.e. UL 489 in
the US, and CSA-C22.2 No. 5-02 in
Canada, also do not include any testing
provisions to specifically verify the
circuit breaker’s performance as a
motor protective device. In order to
establish the circuit breaker as a motor
protective device, the breaker must first
be listed under the UL 489 product
standard, and then pass additional
calibration testing per the industrial
control standard, UL 508 [1]. In Canada,
the same situation would apply, with
additional motor overload testing
required per their equivalent standard
for industrial control equipment,
CSA-C22.2 No.14. It can thus be said
that, world-wide, a molded case circuit
breaker requires additional calibration
per the product standards for
contactors and motor starters in order
to verify its performance as a motor
overload protective switch.
In the IEC world, as well as in North
America, one would typically add a
motor switching contactor to a circuit
breaker in order to provide motors with
the added capability of remote
switching, as well as a higher switching
frequency and a longer electrical life for
the motor starter. In the IEC world,
these motor starters would predominently consist of two components, i.e.
a circuit breaker or motor protective
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switch for motor overload and shortcircuit protection, and a motor
contactor for direct switching purposes.
In North America, on the other hand,
combination motor starters are still
overwhelmingly made up of at least
three power circuit components in the
motor branch circuit.
North American combination
motor starters are mainly 3
component assemblies
Whereas it is common to find circuit
breakers additionally calibrated for
motor overload protection in global
regions dominated by IEC standards, in
North America circuit breakers are still
commonly combined with separately
mounted overload relay protective
devices conforming to UL 508 and
CSA-C22.2 No.14 in motor starter
circuits. Thus, the prevalent combination motor starter configuration in
the US and Canada consists of at least
three power circuit components, a
number not unlike the combination of
fuses, contactor and motor overload
relay still very commonly encountered in
the IEC world for motor circuits. In both
cases, the circuit breaker or fuse fulfills
the role of branch circuit protective
device (BCPD) for the branch circuit. A
typical IEC motor protective device, e.g.
a Moeller PKZM0, is referred to as a
motor protective switch or manual
motor controller in North America.
Manual motor controllers certified per
UL 508 and CSA-C22.2 No.14 standards
are not suitable as branch circuit
protective devices (BCPD) per the
electrical codes. In a motor branch
circuit, they would require the
additional presence of a BCPD such as a
circuit breaker or fuse [2]. They can
fulfill the role of a BCPD for individual
motor branch circuits if they are
additionally evaluated as Type E selfprotected controllers, in which case they
would also require the provision of an
additional terminal block on their
UL 489 Inverse Time Circuit Breaker, with adjustable or,
more commonly encountered, fixed overload response
trips. (UL 508 Table 76.2,
Construction Type C)
incoming supply side to achieve the
necessary electrical clearances. In that
capacity they can also be combined with
conventional magnetic contactors for
certification as Type F combination
motor controllers.
Two common types of combination
starters encountered in North America
include a circuit breaker as the overcurrent protective device along with a
motor switching contactor and a
separately mounted overload relay. The
first, and most common, features an
Instantaneous-Only Trip circuit breaker
as the protective device and accounts for
the great majority of circuit breaker type
combination motor starters in the North
American industrial sector. The other
form of circuit breaker type combination
starter would feature an inverse time
circuit breaker, most likely with a fixed
overload response setting (Figure 1).
Circuit breakers with a fixed overload
response capability are very seldom
UL 489 Motor Protective Circuit Breaker, with
adjustable overload trip, with UL 508
calibration, without separate overload relay
UL 489 Instantaneous
Trip Circuit Breaker,
without overload trips
(UL 508 Table 76.2,
Construction Type D)
Figure 1: In North America, combination motor starters still predominently consist of at least 3 main power circuit components. The
new motor protective circuit breaker Type NZM..2-ME..-NA allows for a 2 component combination motor starter solution consisting of
the circuit breaker and a motor switching HP rated contactor.
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have been tested and certified together
as a motor starter assembly.
The main disadvantages of a 3 component motor starter solution from an IEC
point of view, include an obvious
greater need for volume to house the
assembly, as well as more elaborate
mounting and wiring considerations. In
the case of an inverse time breaker,
there is the additional aspect that the
breaker and the motor overload relay
would now double the heat produced
in the enclosed housing space through
normal component power losses.
The advantages of a 2
component combination motor
starter solution
FIgure 2: Modern design 2 component combination motor starter solutions for the North
American market: UL 508 Type F – Combination Motor Starters, consisting of a PKZM0
manual Type E self-protected combination motor controller combined with a DIL M motor
switching contactor. The pictured starters are mounted on busbar adapters directly fed
from a busbar system. As a Type E device, the PKZM0 is also equipped with an incoming
supply terminal (circled in red) featuring the larger electrical distribution clearances.
encountered in the IEC world, and are
mostly found in Asia or in the residential market. The need for a circuit
breaker with fixed response settings
would more likely arise in non-motor
load applications and would probably
tend to feature larger currents and long
cable lines, for which a closer match of
the load ampacity to the breaker’s fixed
setting would be useful in keeping
down material costs, such as copper
content. A circuit breaker with an
adjustable overload or long time
response, on the other hand, would
always have to be connected to a
conductor whose ampacity would be
equal to, or greater than, the circuit
breaker’s maximum adjustable current
setting, and could thus potentially lead
to higher overall installation costs. In
the IEC world, instantaneous-only trip
circuit breakers are occasionally used
for motors with unusually long starting
times, and combined with a separately
provided electronic motor overload
relay on which various trip class settings
can be selected to better match the
load. Instantaneous Trip-only circuit
breakers are certified in North America
as Recognized Components only. This
type of certification is by definition
restrictive, and subject to additional
conditions of acceptability in order to
meet the requirements of the North
American electrical codes. In the case of
these circuit breakers, this would
primarily involve the need to always
apply them with a dedicated motor
contactor and overload relay which
Figure 3: The motor protective circuit
breaker NZM2-ME-NA, listed per UL 489
and certified per CSA-C22.2 No. 5-02, has
additionally been evaluated per the motor
overload calibration requirements of UL
508 and CSA-C22.2 No. 14. In addition
to the adjustable overload and instantaneous short circuit trip adjustments, the
device has a motor inrush trip class selection feature similar to the ones available
in premium design overload relays.
Moeller offers 2 component combination motor starters in the form of
UL 508 listed Type F combination
controllers for current ranges up to
52A. They are especially popular since
they can also be mounted and wired in
arrays on modern space saving busbar
adpaters for control panel applications
(Figure 2) [2, 3]. Moeller has introduced
a new molded case circuit breaker, Type
NZM..2-ME...-NA, with a built-in motor
overload protective function (Motor
Protective Circuit Breaker) for motor
full load currents in the range of
45...200A. The circuit breaker is also
certified and was developed at the
same time as the North American
standards and testing requirements for
this type of protective device were
being formulated. The breaker is
„UL-Listed“ and „CSA-Certified“. In
Moeller’s line it’s a size 2 frame construction breaker, and it is equipped
with an electronic trip unit. These larger
NZM..2-ME…-NA „motor protective
switches“ also feature a much broader,
and overlapping, adjustable setting
range (Figure 3). Only three separate
devices are required to cover the entire
45A to 200A motor full load current
setting range (Table 1). The current
values correspond to North American
motor HP ratings from 60 through
150HP @ 460/480VAC. The instantaneous short circuit trips are adjustable
and can be set in a broad range
between 2 ... 14 x In in order to
accommodate typical motor inrush
currents and prevent nuisance tripping.
A special feature of this breaker is its
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Motor Protective Circuit Breakers for North America (Inverse Time Circuit Breakers)
Circuit Breakers with adjustable electronic trips for motor overload and short circuit protection.
Listed to UL 489 und certified to CSA -C22.2 No. 5-02, also IEC rated and CE marked.
Motor overload trip calibration per UL 508 and CSA C22.2 No.14
Additional time delay setting, incremental between 2 and 20 seconds, to adjust for motor inrush at 6 x Ir
UL/CSA 100 % rated circuit breakers
Setting Range
short circuit trip
Max. HP
460 V
480 V
Breaker with Normal
Interrupting rating
Breaker with High
Interrupting rating
575 V 85 kA 240 V
600 V 35 kA 480 V
25 kA 600/347 V
Suitable motor
switching contactor
150 kA 240 V
100 kA 480 V
50 kA 600/347 V
In = Iu
Ir [A]
Ii [A]
2 ... 14 x In 60
2 ... 14 x In 100
2 ... 14 x In 150
Ratings in the latest Moeller main catalog are binding!
Table 1: Circuit breakers with adjustable overload and short circuit trips, and additional evaluation per the motor overload calibration
requirements of the industrial control standards UL 508 and CSA-C22.2 No.14, are destined to become in North America the larger versions of popular motor protective switches. These breakers will be typically combined with remotely operable electro-magnetic motor
switching contactors for long life combiantion motor starter applications. The circuit breakers are also 100% rated, so that the full
range of their adjustability can be utilized.
100% rating. Conventional circuit
breakers in North America are normally
rated at 80%, which means that a
circuit breaker serving a continuous
load can only be operated up to 80% of
its current rating.
100 % rated Circuit Breakers, on the
other hand, can be set to up their
maximum rating, which in the case of
this motor protective circuit breaker
would correspond to the motor’s full
load current. Circuit breakers which
have been certified for 100% rating in
North America are all marked
accordingly, whereas standard 80%
breakers do not have to carry a marking
to this effect. These motor protective
circuit breakers represent a significant
improvement in Moeller’s range of
molded case circuit breakers for the
North American market and constitute
an important step in the effort to
achieve world market rated assemblies,
such as control panels for global
applications, which would share
identical layouts and bills of material.
Per the North American electrical codes,
circuit breakers are able to also fulfill
the function of motor controller.
However, it is much more typical and
useful to combine them with motor
switching contactors in motor starter
applications in order to provide the
starter with both a remote operational
capability and a much longer electrical
lifespan. The circuit breaker is better
suited as the main disconnect and
protective device in these applications.
Of course, motor reversing applications
can also be easily accommodated with
the use of an additional contactor to
configure a reversing combination
motor starter assembly. Thus, the
availability of 2 component combination
motor starters for motor rated currents
up to 200A easily covers the very large
majority of motors encountered in
today’s modern industrial environment.
The motor protective breaker and
contactor combinations have been
listed as „Combination Motor Starters“
with two levels of Short Circuit Current
Ratings (SCCR) to provide a broader and
more flexible range of values for
industrial control panel applications.
Motors with full load rated currents
extending beyond 200A are encountered much less frequently than small
motors so that, relatively speaking, 3
component combination motor starters
can still be applied for larger motors
without too great of an additional cost
burden for the installation. The new
motor protective circuit breakers also
carry IEC ratings and bear the important
CE mark for applications within the
European Union. They are thus equally
suitable as motor protective devices in
countries subject to compliance with IEC
standards. IEC compliant circuit breakers
for motor protection are, in fact,
available for motor rated currents up to
With grateful acknowledgment of the
support from:
Mr. Andre R. Fortin, BA Phys.
Manager – Codes & Standards
International Corporate Advisor –
Power Products
Moeller Electric Corporation,
Millbury, Massachusetts, USA
Mr. Dieter Reiß, Dipl.-Ing. Approvals,
Institute for International Product
Safety GmbH, Bonn
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„Schaltgeräte und Schaltanlagen für den
Weltmarkt und für den Export nach
Article No. 110188
„Components and Systems suitable for
World Markets and Export to North
Article No. 110189
Moeller GmbH, Bonn, 2007
Wolfgang Esser
„Besondere Bedingungen für den Einsatz
von Motorschutzschaltern und
Motorstartern in Nordamerika“
Article No. 267951
„Special considerations governing the
application of Manual Motor Controllers
and Motor Starters in North America“
Article No. 267952
Moeller GmbH, Bonn, 2003
Wolfgang Esser
„Sammelschienenadapter für die rationelle
– jetzt auch für Nordamerika –“
Article No. 110774
„Busbar Component Adapters for modern
industrial control panels“
Article No. 110775
Moeller GmbH, Bonn, 2007
Wolfgang Esser
„Leistungsschalter für den Einsatz in
Article No. 285780
“Molded Case Circuit Breakers, for
applications in North America”
Article No. xxxxx
Moeller GmbH, Bonn, 04/2008
Moeller addresses worldwide:
E-Mail: [email protected]
Internet: www.moeller.net
Issued by Moeller GmbH
Hein-Moeller-Str. 7-11
D-53115 Bonn
© 2008 by Moeller GmbH
Subject to alterations
VER1200+2100-967en ip 07/08
Printed in Germany (07/08)
Article No.: 118983
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